Abstract

We report here an improved efficiency, up to 4.8% with a high fill factor of under AM 1.5G spectral illumination and intensity, for poly(3-hexylthiophene) and [6,6]-phenyl butyric acid methyl ester bulk heterojunction photovoltaic (PV)devices with a 1:0.8 weight ratio using surface modifications to the indium tin oxide (ITO) anodes through plasma oxidized silver. Here, an enhanced short-circuit current density was achieved without significant loss in the open-circuit voltage nor the fill factor , leading to an efficiency jump from 4.4% in the control devices to 4.8% with the surface modified ITO anode. The enhanced short-circuit density is attributed to an interface energy step between the ITO and the polymer hole transporting layer. It has been theorized that the introduction of an interface energy step could alter the charge collection efficiency, resulting in an improved overall efficiency in PVdevices. In our study, the current density–voltage characteristics under darkness clearly show an increased current density, especially under forward bias, for the anodetreated cell, suggesting the presence of an interface energy step between the ITO and the hole transporting layer with surface modified ITO anodes.

Received 08 November 2007Accepted 10 December 2007Published online 07 January 2008

Acknowledgments:

The authors would like to thank Steven A. Ringel and Maria Gonzalez for supplying the calibration PV devices, Malcolm H. Chisholm, Yi-Hsuan Chou, and Yagnaseni Ghosh for optical measurements, and James Jones for help with equipment maintenance. This work was supported by the Center for Photovoltaics Innovation and Commercialization (PVIC) and the Institute for Materials Research (IMR).

Abstract

We report here an improved efficiency, up to 4.8% with a high fill factor of under AM 1.5G spectral illumination and intensity, for poly(3-hexylthiophene) and [6,6]-phenyl butyric acid methyl ester bulk heterojunction photovoltaic (PV)devices with a 1:0.8 weight ratio using surface modifications to the indium tin oxide (ITO) anodes through plasma oxidized silver. Here, an enhanced short-circuit current density was achieved without significant loss in the open-circuit voltage nor the fill factor , leading to an efficiency jump from 4.4% in the control devices to 4.8% with the surface modified ITO anode. The enhanced short-circuit density is attributed to an interface energy step between the ITO and the polymer hole transporting layer. It has been theorized that the introduction of an interface energy step could alter the charge collection efficiency, resulting in an improved overall efficiency in PVdevices. In our study, the current density–voltage characteristics under darkness clearly show an increased current density, especially under forward bias, for the anodetreated cell, suggesting the presence of an interface energy step between the ITO and the hole transporting layer with surface modified ITO anodes.